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Ch. 7 - Transcendental Functions
Hass - Thomas' Calculus 15th Edition
Hass15th EditionThomas' CalculusISBN: 9780137616077Non è quello che usi tu?Cambia libro di testo
Capitolo 7, Problema 7.2.61

In Exercises 57–70, use logarithmic differentiation to find the derivative of y with respect to the given independent variable.
61. y = √(θ + 3) sin θ

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Start by expressing the function clearly: \(y = \sqrt{\theta + 3} \sin \theta\). Recognize that this is a product of two functions of \(\theta\): \(u(\theta) = \sqrt{\theta + 3}\) and \(v(\theta) = \sin \theta\).
Rewrite \(y\) in a form that is easier to differentiate logarithmically: \(y = (\theta + 3)^{\frac{1}{2}} \sin \theta\).
Take the natural logarithm of both sides to apply logarithmic differentiation: \(\ln y = \ln \left( (\theta + 3)^{\frac{1}{2}} \sin \theta \right)\).
Use logarithm properties to separate the terms: \(\ln y = \frac{1}{2} \ln (\theta + 3) + \ln (\sin \theta)\).
Differentiate both sides with respect to \(\theta\), remembering that \(\frac{d}{d\theta} (\ln y) = \frac{1}{y} \frac{dy}{d\theta}\), and apply the chain rule and derivative rules for logarithms and trigonometric functions.

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Logarithmic Differentiation

Logarithmic differentiation is a technique used to differentiate functions that are products, quotients, or powers of functions by taking the natural logarithm of both sides. This simplifies the differentiation process by converting multiplication into addition and powers into products, making it easier to apply derivative rules.
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Logarithmic Differentiation

Product Rule

The product rule is a fundamental differentiation rule used when finding the derivative of a product of two functions. It states that the derivative of f(θ)g(θ) is f'(θ)g(θ) + f(θ)g'(θ), which helps in differentiating expressions like y = √(θ + 3) sin θ.
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The Product Rule

Chain Rule

The chain rule is used to differentiate composite functions, where one function is inside another. For example, when differentiating √(θ + 3), the chain rule helps by differentiating the outer function (square root) and multiplying by the derivative of the inner function (θ + 3).
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Intro to the Chain Rule